This invention relates to processes for the scrubbing of noxious substances from exhaust gas stream, particularly those found in the semiconductor industry.
Large quantities of noxious substances are employed in the semiconductor industry in the processing of electronic wafers/chips and other devices. These include a variety of compounds of Group 3, 4 and 5(b) elements of the Periodic Table and in particular hydrides of such elements, for example silane (SiH.sub.4), phosphine (PH.sub.3), arsine (AsH.sub.3), geranium hydride (GeH.sub.4) and boron hydride (B.sub.2 H.sub.6). Such hydride gases are commonly pyrophoric and toxic; their uncontrolled release from semiconductor processing chambers in exhaust gas streams would lead to a number of problems including blocking the chamber ducts, fire hazards, corrosion of the processing apparatus and a visible plume from the exhaust stack of the apparatus.
Traditional dosed water scrubbing methods have generally been found to be problematic in that the by-products are generally solid and precipitate to cause blocking of the apparatus. In cases in which the wet scrubber is dosed with an oxidiser or a base, the scrubbing method generally suffers from a poor rate of reaction between the solution and, for example, the insoluble silane and this condition is exacerbated by a lack of solubility of the reaction by-products.
There is therefore a need for an improved scrubbing process for such noxious substances.